During the 40 weeks of pregnancy gestation, there will be a wealth of tests offered to mom in order to predict the chances of baby being born with a birth defect. One such test is the quad marker screen. The quad marker screen is a blood test that will help to recognize the “chance” of baby having a birth defect.
It is important for parents to understand that the quad marker screen is not a tool to diagnose a baby with a birth defect. The screen simply offers a percentile chance of the baby having a birth defect. The test results can come back positive for babies that have no increased risk of birth defects and on the other side of the coin, can come back negative for babies who are later born with birth defects. It is important to think about the possibility of a false positive when choosing whether or not to have the quad marker screen test performed.
What Can the Quad Marker Screen Predict?
During the testing process, a small amount of blood is drawn from the pregnant mom. This blood is tested for alpha-fetoprotein, unconjugated estriol, human chorionic gonadotropin and inhibin-A.
- Alpha-fetoprotein is a protein produced by the liver of the fetus.
- Unconjugated estriol is a protein produced in the liver of the fetus as well as the placenta.
- Human chorionic gonadotropin is a hormone produced in the fetal placenta.
- Inhibin-A is also a hormone produced in the fetal placenta.
The resulting levels of the proteins and hormones are calculated and based upon those levels the risk factor for a birth defect are reported. Neural tube defects, twin pregnancy, and Down’s syndrome are all associated with varying levels of proteins and hormones.
When Is the Quad Screen Marker Offered?
The quad screen marker can only be performed between the 15th and 20th week of pregnancy. Due to the short time frame for testing, the doctor and nurses in the office where you are receiving care may ask more than one time if you would like to have the quad screen marker testing run. In some offices, mothers are required to sign a release if they do not want to have the test completed.
The Efficacy of the Quad Marker Screen
The results of the quad marker screen are far from 100% accurate. The test predicts the presence of an open neural tube defect in approximately 75% of all cases. Fetuses with a high risk of Down’s syndrome are accurately reported in more than 80% of all cases with 75% of Down’s syndrome cases being detected in mother’s under the age of 35.
What Happens After a Positive Result?
After the quad screen marker tests report a higher risk of possible chromosome defects, the mother will be offered more invasive testing to determine the health of the baby. These tests may include an amniocentesis and / or chorionic villus sampling.
The quad marker screen is simply a tool for further care for baby. Some parents simply do not believe they need to know the results, while others want to make sure baby is 100% healthy. The choice lies with the parents.